This invention relates to a lithographic process for fabrication of a large scale integrated circuit by exposure to a beam of electron and more particularly to a lithographic process in vapor phase comprising formation of a plasma-polymerized photoresistive film, exposure of the film to electron beam and development of the exposed part of the film.
In recent years, there has been an increasing interest in the application of electron beam lithography to so-called "submicron fabrication" in the fabrication of highly integrated devices including integrated circuits. In this connection, many attempts have been made to develop electron-beam sensitive materials suitable for use in electron-beam lithography.
As a result of our close studies on the lithographic process by means of electron beams which can be carried out in a unified vacuum system, we have now found that the electron-beam sensitive film of a polymer, especially polymethyl methacrylate produced by so-called plasma polymerization technique can be suitably used in the lithographic process by exposure to a beam of electrons. This invention has been established by the association of the plasma polymerization and the electron-beam exposure with subsequent development by etching in vapor phase.
A main object of this invention is to provide a lithographic process by which the consecutive steps of formation of a plasma-polymerized film, exposure of the film to electron beams and development can be carried into effect in vapor phase under vacuum or reduced pressure within a unified vacuum apparatus.
Other objects and advantages of the invention will become apparent from the following descriptions.